The invention relates to a method for controlling an apparatus for preparing items to be mailed, comprising a plurality of successive stations, a central data processor, a plurality of data processors each associated with a station, and a data channel by means of which the processors are connected, in which method communication between the data processors associated with stations and at least the central data processor occurs via said data channel, and the data processors each associated with a station are selectively activated for communication via the data channel in response to given control signals.
Such a method is known from U.S. Pat. No. 4,547,856.
U.S. Pat. No. 3,606,728 discloses an apparatus for preparing items to be mailed, comprising a plurality of successive stations, which can be controlled depending on processing instructions stored in a data processor. Each station is connected to the data processor via a separate line. This involves the drawback that a great deal of cabling is necessary, which, moreover, must be specifically adapted to the configuration of the apparatus.
In the method known from the above-mentioned more recent U.S. Pat. No. 4,547,856, the control signal is formed by an address signal, which is transmitted via a bus. The address signal activates a data processor associated with a station for receiving a control signal, when this address signal corresponds with the address code stored in that processor. Data regarding the configuration of the apparatus are recorded in a PROM installed in the apparatus.
With this form of communication, not every processor associated with a station requires a separate connection with the central processor, so that the cabling can be of relatively simple design and the apparatus can be built up of modules. It is a drawback, however, that in case of modification of the configuration an adapted PROM must be installed and that disturbance may be caused by errors made in assigning addresses to the processors associated with the stations and in programming the PROM accordingly.
The even more recent European patent application 0,376,738 discloses a method for controlling an apparatus for preparing items to be mailed, in which method the stations communicate with previous and succeeding, adjacent stations via a one-directional and a two-directional bus and communicate directly with a central processor via a third bus. The configuration of the apparatus is determined at start-up by transmitting a data base in one direction along the data processors of successive stations, each adding its respective identification data to the base. The configuration of the apparatus appears from this data base and the order of the identification codes therein. An advantage of this apparatus over the other systems discussed above is that in case of modification of the configuration, the data base regarding the configuration automatically adapted.
However, a drawback of the method described in European patent application 0,376,738 is that its implementation requires a complicated communication structure, comprising three communication levels and three buses.